Organic carbodiimides and polycarbodiimides are known. Their chemistry and production are described, for example, in Chemical Reviews, vol. 81 (1981), pp. 589 to 639 and Angewandte Chemie 74 (1962), pp. 801 to 806.
Carbodiimides and polycarbodiimides are preferably used as stabilizers against the hydrolytic cleavage of polyester-based plastics materials, as described, for example in EP-A 0 602 477, U.S. Pat. Nos. 2,853,473, 2,853,518 and 3,502,722. According to DE-A 1 494 009, aromatic and/or cycloaliphatic monocarbodiimides, which are substituted in the 2 and 2′ position are particularly suitable for use as stabilizers. Polycarbodiimides having a molecular weight of over 500 and a content of more than 3 carbodiimide groups are described in DE-A 1 285 747 as stabilizers against the effects of heat and humidity in ester group-containing plastics materials.
Blends of thermoplastic molding compositions are arousing increasing interest in engineering, as new customized property profiles can be attained by the mixing of known polymers. Only a few of the known thermoplastic molding compositions are, however, miscible with one another. The majority of thermoplastic molding compositions are not miscible without further measures. In most cases, at least partial miscibility is, however, necessary for the optimal attainment of properties.
Various generally known methods can be used to improve miscibility. The mixing of polymers in the molten state only results in a homogeneous blend in compatible polymers. Another method is graft polymerization: the polymerization of monomers onto an existing polymer. This method is limited to a few monomers and can be carried out only with special equipment.
Another method for improving the miscibility of thermoplastic molding compositions is the use of compatibilizers. These react chemically with the two blend components in the production of the blend, and thus result in improved miscibility. A known method is the use of maleic anhydride or, as described in DE-A 19 739 686, the use of bisoxazolines as a compatibilizers. The known compatibilizers can, however, only be used on a few blends of thermoplastic molding compositions. Explosive peroxides must, at the same time, also be used to produce blends using maleic anhydride, which causes production costs to rise.
In the technical journal Gummi Fasern Kunststoffe GAK 5/2001, p. 299, Title: “Reaktives Blenden von unverträglichen Kunststoffen am Beispiel von Polyamid und Polyestern” [“Reactive blending of incompatible plastics materials, using the example of polyamide and polyesters”], the difficulty of reactive extrusion by means of the functionalization (degradation) of the polyamide in one extrusion stage, and the actual reactive blending process by means of transesterification and coupling of the blend in a second extrusion stage, is apparent. There is also a technical difficulty present, i.e. that the required arrangement of two twin-screw extruders is not readily available, and that difficulties occur in exact process control owing to the degradation of the polyamide with the subsequent transesterification of the PET.
The object of the present invention was to provide compatibilizers that are universally and cost-effectively suitable for producing blends of thermoplastic molding compositions, and thus to make possible the preparation of these blends.